This invention relates generally to thermoplastic products with an absorbing agent entrained therein. More particularly the invention relates to a product of manufacture formed from a thermoplastic material that has an absorbing agent concentrated towards the surface of the product, wherein preferably a concentration gradient of the absorbing agent exists. The invention also relates to a process of manufacture of an absorbent polymeric material, formed as a product, comprising mixing a thermoplastic material with an absorbing agent, and forming the moisture absorbent polymeric product such that the absorbing agent is primarily concentrated toward the surface of the product, wherein preferably a concentration gradient of the absorbing agent to absorb moisture exists.
Many moisture-sensitive products must be shipped and stored in conditions that are as free from moisture as possible. For example, medications and diagnostic test strips often lose some of their efficacy after prolonged exposure to moisture and are preferably shipped and stored in moisture free environments. Containers for holding such products may be fashioned out of moisture-impermeable material, such as well-known thermoplastics, that resist entry of exterior moisture. However, entry of moisture into such containers is inevitable, either through diffusion or the opening and closing of the container, thereby exposing the product to humidity. In the case of medications, the end-user often opens the plastic container repeatedly in order to obtain just one dosage, exposing the remaining dosages to undesirable moisture-bearing air. Therefore, such containers preferably include means to absorb any moisture that enters the container before it affects the moisture-sensitive product inside.
Other items, such as food or other organic products, may actually release moisture after being placed within a container or sealed packaging, and if the packaging is substantially moisture-impermeable, then the moisture will remain in close contact with the product. In many cases this released moisture may actually be damaging to the product that released the moisture. In this instance, some desiccating means is preferably included in the packaging to absorb this released moisture and maintain a relatively dry environment.
Still other items, such as electronic components, may require a substantially moisture-free environment during shipment and storage to provide optimal performance. Such items are typically shipped in virtually moisture-impermeable containers, but the presence of initially trapped moisture, or the seepage of moisture over time, could still affect performance of such products. Once again, a desiccating means is preferably included in the shipping container that will absorb moisture, while not having an effect on the other components.
In order to absorb such excess moisture and protect the contained products, desiccating materials have been introduced into the interior of containers. These desiccants are usually in the form of powders or granules and therefore must be contained in some manner to prevent contamination of the product. Previous attempts to introduce desiccants to such containers have included the use of bags and packets formed from breathable materials, perforated plastic canisters, desiccant tablets and aerated plastic cartridges with the desiccant inside. These containers are problematic, however, as any breakage would release the desiccant freely into the container. Also, these desiccant containers can release some amount of dust originating from the desiccant fill and adversely effect the product to be protected from moisture. Other solutions involve the creation of a separate compartment within the container to hold the desiccant (for example in a desiccant filled stopper for a tube, or a side compartment within the tube), but such a compartment typically limits the moisture-to-desiccant contact and reduces the absorption rate. There is also the ever present danger of damage to the side compartment which will also release desiccant into the main container.
Thus, there is a need for a means of introducing an absorbing agent into a plastic container or other article of manufacture while preventing the absorbing agent from being released and potentially contacting the moisture-sensitive product. One means for accomplishing this goal is entraining the absorbing agent directly into a plastic structure, such that the desiccant cannot be released. A problem inherent in such structures, however, is that once the absorbing agent is entrained within the plastic, it has extremely limited contact with the outside moisture.
It is accordingly a primary object of the invention to provide an absorbing agent-entrained polymeric product that provides an effective amount of moisture-to-absorbing agent contact, preferably and surprisingly, without the use of wicking fibers.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.